there is a company called jamison brass and ammunition. if you would go on there website you will see the large  number of cases    that they manufacture. don't laugh too hard when you see that  many of them can be eaisly formed from a parent brass. they also produce many obsolete straight wall cases that there can't be the demand that there is for 30-40. i e-mailed them a couple months ago stating pretty much what i'm writing now. as you would  suspect; no reply. they are"missing the boat"
on another note in a search for brass. going on the shooting websites has pretty much dried up the supply. use alternative site searches. i live in pa. there is a site called pennswoodsclassified.net. i ran a ad it the reloading and ammunition section and got 2 hits that resulted in 45 pieces 18 factory loaded. another site; this one for trapshooters (which i am) also yeilded 2 hits. one for 250 pieces. the other for 1loaded factory rem. box and the mate that was a once fired box. what i'm suggesting is try other  avenues. how about an ad in the local newspaper, the bulliten board at the gunclub ( most shooters don't know how scarce this stuff is